Overloading in Perl / Number::Fraction

Number::Fraction constructor (cont)

•  } elsif (@_ == 1) {
      if (ref $_[0]) {
        if (UNIVERSAL::isa($_[0], $class) {
          return $class->new($_[0]->{num}, 
                             $_[0]->{den});
        } else {
          croak "Can't make a $class from a ", 
            ref $_[0];
        }
      } else {
        return 
          unless $_[0] =~ m|^(\d+)/(\d+)|;
  
        $self->{num} = $1;
        $self->{den} = $2;
      }